Tubetech SMC2B noisy

[Niketouille]

Hi,
One of my client has a Tubetech SMC2B with one noisy channel.
Does anybody have access to a schematic or a service manual ?
I contacted Tubetech but they doesn't want to help.

Cheers
Nkt

 

[ruairioflaherty]

First test is to swap tubes between channels, if the problem follows the tube you've found your culprit (very common in tube gear).

 

[Niketouille]

Hi,
Thanks, but I already did that. I am suspecting some kind of noisy cap somewhere. As I am a bit lazy I like to have a manual to easily trace signals. I guess I will have to swap signal path at some point.
Cheers

 

[ruairioflaherty]

Bummer! Sometimes you get lucky, sometimes not 

 

[outoftune]

inspect the PCB for cracks / stress...i've seen some tube tech units that have damage to the PCB from heat.

there are a lot of ICs and transistors on the front panel for the sidechain and multiband crossover etc.

i have repaired a lot of tubetech units. since one channel seems to be fine, it doesn't seem like its the PSU, but double check the 270/240vdc and the lower voltage supplies that run the IC's / transistors.

i had one of these units recently that had an intermittent level fluctuation...after a lot of back and forth and multiple trips in/out of the shop, the issue was traced to the surface mount resistors on the output gain level...i resoldered those and the issue vanished.

 

[Niketouille]

Hi,
Thanks for all the advice.
It was a combination of bad tubes and noisy psu.
Psu caps value were going down with the aging/temperature and as a result serie resitor in the psu run hot.
Changed all that and now it runs fine.
Cheers guys
Nkt